Three‐Phase‐Heterojunction Cu/Cu2O–Sb2O3 Catalyst Enables Efficient CO2 Electroreduction to CO and High‐Performance Aqueous Zn–CO2 Battery

Abstract Zn–CO2 batteries are excellent candidates for both electrical energy output and CO2 utilization, whereas the main challenge is to design electrocatalysts for electrocatalytic CO2 reduction reactions with high selectivity and low cost. Herein, the three‐phase heterojunction Cu‐based electrocatalyst (Cu/Cu2O‐Sb2O3‐15) is synthesized and evaluated for highly selective CO2 reduction to CO, which shows the highest faradaic efficiency of 96.3% at −1.3 V versus reversible hydrogen electrode, exceeding the previously reported best values for Cu‐based materials. In situ spectroscopy and theoretical analysis indicate that the Sb incorporation into the three‐phase heterojunction Cu/Cu2O‐Sb2O3‐15 nanomaterial promotes the formation of key *COOH intermediates compared with the normal Cu/Cu2O composites. Furthermore, the rechargeable aqueous Zn–CO2 battery assembled with Cu/Cu2O‐Sb2O3‐15 as the cathode harvests a peak power density of 3.01 mW cm−2 as well as outstanding cycling stability of 417 cycles. This research provides fresh perspectives for designing advanced cathodic electrocatalysts for rechargeable Zn–CO2 batteries with high‐efficient electricity output together with CO2 utilization.


Supplementary Experimental Section 1. Preparation of the Electrode
The work electrodes were typically prepared as follows: 8 mg catalyst, 1900 μL isopropanol, and 100 μL Nafion solution (5.0 wt%) were mixed and ultrasonicated for one hour until a homogeneous ink was obtained.Subsequently, the ink was evenly spread over the carbon paper with a catalyst loading of ~1 mg cm −2 .

Evaluation of TOF
The turn over frequency (TOF) for CO was calculated as follows: where jCO is the partial current density for CO production (A cm -2 ), S is the surface area of working electrode (1×1 cm 2 ), n is the number of electron transferred for product formation (n=2), F is Faraday constant (96485 C mol -1 ), mcat is the catalyst mass in the electrode (g), w is Cu loading in the catalyst, and MCu is the atomic mass of Cu (63.5 g•mol -1 ).

Figure S10. 1 H
Figure S10. 1 H NMR result for the liquid products of the CO2RR for Cu/Cu2O-Sb2O3-15 electrode at a potential of -1.3 V vs. RHE.

Figure S11 .
Figure S11.Comparison of CO faradaic efficiency of Cu/Cu2O-Sb2O3 series catalysts with different chemical compositions (icons are shown below).

Figure S12 .
Figure S12.Comparison of the partial current density of Cu/Cu2O-Sb2O3 series catalysts with different chemical compositions.

Figure S14 .
Figure S14.FEs of H2 for the main electrodes at different potentials.

Figure S15 .
Figure S15.Partial current density of H2 for the main electrodes at different potentials.

Figure S19 .
Figure S19.(a) LSV curve of Cu/Cu2O-Sb2O3-15 in H-type cell and flow cell at a scan rate of 5 mV s -1 .(b) Faradaic efficiency (c) Partial current density of CO for Cu/Cu2O-Sb2O3-15 in H-type cell and flow cell.(A flow cell equipped with a GDE device was applied for CO2RR.A commercial Pt electrode was used as an anode and an Ag/AgCl acted as the reference electrode.1 M KOH aqueous solution was utilized as electrolytes, which were separated by a piece of anion-exchange membrane.

Figure S24 .
Figure S24.Optical image of an electronic clock powered by the reversible aqueous ZCB with Cu/Cu2O-Sb2O3-15 cathode.

Figure S30 .
Figure S30.Digital photograph of in situ ATR-IR device.

Table S2 .
Actual molar ratios of Sb/Cu and actual metal loadings on the catalysts were measured by ICP-OES analysis.

Table S3 .
The amount of each phase in the three-phase heterojunction Cu/Cu2O-Sb2O3-15 catalyst was calculated from XRD data.

Table S4 .
Summary of the reported Cu-based electrocatalysts for CO2 electro-reduction reaction to CO in recent years with H-cell.

Table S5 .
The formation energy of Sb-O doped Cu/Cu2O with different doping sites.